Zero emission liquid fuel production by oxygen injection

ABSTRACT

An enhanced oil recovery method is provided. This method includes; introducing a first essentially pure oxygen stream into a subterranean hydrocarbon-bearing formation traversed by at least one injection well and at least one production well, and initiating and sustaining in-situ combustion in the vicinity of the injection well. This method also includes introducing a second essentially pure oxygen stream and a hydrocarbon-containing fuel gas stream into the combustion device of a power generation system, wherein the combustion device produces an exhaust gas stream comprising water and carbon dioxide. This method also includes separating the exhaust gas stream into a stream of essentially pure water, and a stream of essentially pure carbon dioxide, and introducing at least a portion of the essentially pure carbon dioxide stream into the subterranean hydrocarbon-bearing formation prior to initiating the in-situ combustion.

The present application is a divisional application of U.S. applicationSer. No. 12/429,250 filed Apr. 24, 2009 and claims the benefit of U.S.Provisional Application No. 61/048,673, filed Apr. 29, 2008, hereinincorporated by reference in its entirety for all purposes.

BACKGROUND

Since 2002, there has been a general trend of increasing oil prices.This trend is generally expected to continue as a result of a number offactors: increasing oil demand from emerging economies; geopoliticalinstability in important production areas; and reduced exploration andtechnological development within the last two decades due to low oilprices.

Current oil prices, along with international regulations on CO2emissions (such as the Kyoto Protocol and beyond, Alberta “carbon tax”,California regulation on GHG footprint of fossil fuels, etc.) increasesthe industries interest in providing innovative solutions that willallow: the increase of oil recovery from a given existing reservoir at areduced additional cost; reliable performance within a large range ofoil/reservoir characteristics; and the reduction of carbon footprint oftechnologies for enhanced oil recovery.

The techniques to be employed for oil recovery depend on the particulargeological conditions (thin reservoirs . . . , porous reservoirs . . . )and are typically performed at different stages of the oil production.

The term Primary Recovery Technologies includes recovery strategiesusing the natural energy of reservoirs. These technologies are based onthe immiscible fluids displacement, and different mechanisms arepossible, such as: Gas Cap drive (expansion of the gas phase); SolutionGas Drive (ex-solution of solved Gas); Bottom Water Drive (aquiferdisplacement). For conventional oil typical performance for primaryrecovery techniques are around 19% of OOIP (Original Oil in Place): lessfor heavy oils, more for light oils.

In the Secondary Recovery, also known as water-flooding, the enhancementof oil production is performed by adding energy to the natural system.Water is typically injected in a well (or a pattern of wells) in orderto maintain pressure in the reservoir and to displace oil towards aproducer. Initially oil alone is produced. Then as water componentprogresses, both oil and water are produced. As time advances, thepercentage of water (the watercut) increases progressively. Forconventional oil, average recovery by Water Flooding is around 32% OIP(Oil In Place) after primary recovery.

Enhanced Oil Recovery (EOR) techniques are used to further increase theamount of recovered oil, in particular when water-flooding is noteffective (or efficient). Some of the various EOR techniques that may beemployed include: thermal-based oil recovery: steam flooding , cyclicthermal injection, in-situ combustion; electric heating, microwavesheating; chemical flooding: polymer flooding, micellar flooding;Immiscible Flooding: Nitrogen injection, CO2 injection; MiscibleFlooding: lean gas injection, CO2 injection; and microbial injection.

For conventional oil, primary recovery is usually followed bywater-flooding, but most of the enhanced oil technologies are not yetcommercially proven. For unconventional oil reserves such as extra heavyoil in Venezuela and Albertan oil sands (characterized by high densitiesand high viscosities (20>API>7, 10000cPo<m<100cPo or 12>API<7,m>10000cPo) primary and secondary recovery are not sufficient toguarantee oil production and the economic exploitation of theseresources is strictly related to the successful development of EORtechnologies. The growing relevance of heavy oils in the world oilreserves and in particular of such unconventional oils results in thedevelopment of new EOR methods.

The SAGD (Steam Assisted Gravity Drainage) is a steam flooding techniqueimproved by the use of two horizontal wells: one for steam injection andone for bitumen extraction. The steam heats the formation increasing theviscosity of bitumen which can flow trough the producer. The maindrawback of SAGD concerns high SOR (steam on oil ratio), ranging from 2to 4. The performance of SAGD are strictly dependent upon reservoirproperties. Characteristics such gas caps, aquifers, and shale in thereservoir can result in uneconomical operations.

Steam flooding and SAGD are typically only efficient for shallowreservoirs (<1000 m) thus not being a viable solution for heavy oilresources in area such as the Arabic gulf and Russia.

The VAPEX (Vapor Extraction) process involves injecting a gaseoushydrocarbon solvent into the reservoir where it dissolves into thebitumen. The bitumen then becomes less viscous and can drain into alower horizontal well and be extracted. The solvent is typicallypropane, butane, or CO2 along with a carrier gas. Main drawbacks of thistechnique are the following. In the case of bitumen or extra heavy oil,blending oil with the solvent without heating the formation producesonly small improvements in oil recovery. Solvent is also expensive, canbe scarce, and therefore the losses in the reservoir can be important.

A number of process such as ES-SAGD, LASER or SAVEX are underdevelopment in order to provide an hybrid in-situ extraction technologycoupling the advantages of steam injection (thermal reduction of oilviscosity) and solvent injection. Lights hydrocarbons are used andsolutions to drawbacks such as reservoir depressurization and solventlosses have to be developed. None of these combine the advantages ofthermal extraction and miscible and immiscible flooding.

The In-Situ Combustion(ISC) process is defined as “the propagation of ahigh temperature front for which the fuel is a coke-like substance, laiddown by thermal cracking reactions”. In recent years, that has been aworldwide interest of ISC for conventional oil.

Compared to mining, SAGD and VAPEX, in-situ combustion based bitumenextraction has the potential to be applied in a wider range of reservoircharacteristics and to provide partially upgraded bitumen with betterthermal efficiency and reduced environmental impact: Benefits of ISCinclude: reduced GHG footprint—50% less than SAGD; almost no waterconsumption; no need for land remediation. Within the ISC, bitumen ispartially upgraded in the underground, and the production is performedby thermal flooding (viscosity reduction) and gas flooding (flue gasdrive).

The use of oxygen injection represents one of the main areas ofdevelopment for this technology. Advantages of oxygen injection forIn-Situ combustion operations include: lower compression cost; simpleignition; better thermal efficiency: produced heat is not dispersedtrough an inert gas; and easier downstream operations: emulsions areeasy to break. Additionally, as in the case of surface oxy-combustion,the use of oxygen will result in the possibility of recovering aCO2-rich stream at the production well, to be used for additional EORand storage. However, low oil prices and lack of GHG emissionsregulations have not justified the use of oxygen in the last twentyyears.

There is a need in society for an in-situ combustion oil recoveryprocess that will improve the economics, improve the oil recovery,reduce the environmental impact, and improve safety.

SUMMARY

The present invention is an enhanced oil recovery method that includes;introducing a first essentially pure oxygen stream into a subterraneanhydrocarbon-bearing formation traversed by at least one injection welland at least one production well, and initiating and sustaining in-situcombustion in the vicinity of said injection well. The present inventionalso includes introducing a second essentially pure oxygen stream and ahydrocarbon-containing fuel gas stream into the combustion device of apower generation system, wherein said combustion device produces anexhaust gas stream comprising water and carbon dioxide. The presentinvention also includes separating said exhaust gas stream into a streamof essentially pure water, and a stream of essentially pure carbondioxide, and introducing at least a portion of said essentially purecarbon dioxide stream into said subterranean hydrocarbon-bearingformation prior to initiating said in-situ combustion.

BRIEF DESCRIPTION OF DRAWINGS

The invention may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, and inwhich:

FIG. 1 is a schematic representation of one embodiment of the presentinvention, with a steam turbine for energy production.

FIG. 2 is a schematic representation of another embodiment of thepresent invention with a combustion turbine for energy production.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is the design of an improved process for enhancedoil recovery based on in-situ combustion. The present invention providesimproved economics due to reduced compression costs, the virtualelimination of N2 in the combustion exhaust, and the reduction of O2requirements. The present invention also provides improved ultimate oilrecovery from oil reservoirs, by combining in-situ combustion and CO2flooding. The present invention provides the dramatic reduction of theenvironmental footprint of oil recovery technologies, with virtuallyzero CO2 emissions, and virtually no water being used. The presentinvention provides improved safety, with CO2 being injected for O2dilution.

The present invention accomplishes this by integrating Oxygen-based insitu combustion for oil recovery, oxycombustion for power-energyproduction, and CO2-flooding.

In one aspect of the present invention, oil production is performed byO2-based in-situ combustion. In-situ combustion off-gas separation isperformed in order to recover a CO2 stream and a fuel gas stream(comprising primarily light hydrocarbons, CO, and H2). The CO2 iscompressed and can be either; partially recycled to the injection well(to improve sweep efficiency and High temperature front displacement);or partially sent to a pipe and used for EOR, ECBM, or storage. Theoxycombustion water is used for additional injection, wet in-situcombustion. The fuel gas is blended with an additional fuel such asNatural Gas and oxy-burned in order to provide power for the compressionof CO2 (for example re-injection, pipeline, etc.).

The present invention of the integration of oxy-combustion withinO2-based in-situ combustion provides improved performance of the in-situcombustion process. This is accomplished by the recovery of a high LHVfuel gas, essentially nitrogen free, in order to reduce NG needs. Thisis also accomplished by the production of a concentrated CO2 stream asthe only gaseous by-product of the process. This results in: thedramatic reduction of the environmental impact of oil upstreamoperations (zero GHG emissions, reduced water needs); the enhancement ofoil recovery performance; and the availability on the oilfield foradditional oil recovery.

Turning now to FIG. 1, enhanced oil recovery system 100 is provided.Essentially pure liquid oxygen stream 101 is introduced and at leastpart of the oxygen is directed into stream 102 is vaporized in vaporizer103 then into oxy-combustion boiler 110. At least part of the oxygen isdirected into stream 104, is increased in pressure in pump 105, andvaporized in vaporizer 106. The pressurized and vaporized oxygen 107 isthen injected into the oil reservoir through an injection well 108 a/108b in order to support in-situ combustion. The pressure at which thevaporized oxygen is introduced into the reservoir may be between about50% and about 80% of the breakdown pressure. A blended stream 111,containing at least oil, gas and water, is recovered from productionwell 112

In another embodiment, the pressurized and vaporized oxygen 107 isinjected into a structure containing a carbonaceous substance such ascoal, petroleum coke (petcoke), or biomass, through at least one inletline 108 a/108 b. A blended stream 111, containing at least oil, gas andwater, is recovered from at least one outlet line 112.

This blended stream is separated in separator 113, thereby producingrecovered oil stream 114, and separated water stream 115. Separatedwater stream 115 may be used as water injection into injection well 108a/108 b. Recovered gas 116, which may include CO2, CO, H2O, CH4, lighthydrocarbons, H2, and H2S, is introduced to separator 117. The exactcomposition of the recovered gas will depend on the nature of theproduced oil and the recovery process itself. The recovered gas will besubstantially free of nitrogen, due to the oxygen injection. Separator117 may include, but is not limited to, the following processes:adsorption, absorption, cryogenic systems and membrane systems. Theadsorption systems may include, but are not limited to, Rectisol,Selexol, or Amine wash systems. In one embodiment, the membrane systemor the combination of cryogenics and membrane system is preferred. Ahigh LHV fuel gas 118, and a stream that is predominantly composed ofCO2 119 are recovered from separator 117. The high LHV fuel gas 118 mayoptionally be further purified in gas purification unit 120. Thepurified high LHV gas 121 may be combined with natural gas stream 109,prior to admission to combustion device 110.

After combusting the oxygen stream 102 with the fuel gas streams (109,121), combustion device 110 outputs power 122 to the process(compression) facility, and also outputs an exhaust stream 123 that ispredominantly H2O and CO2. Impurities may include predominantly SOx, NOxand Oxygen. Exhaust stream 123 enters separator 124, which outputs H2Ostream 125 and CO2 stream 127. The H2O stream 125 is then combined withwater stream 115, thereby producing combined stream 126. Additives canbe used in order to control PH Stream Streams 125 and 126. 126 is thenadmitted into injection well 108 a/108 b. CO2 stream 127 is thencombined with CO2 stream 119, thereby producing combined stream 128which is partially purified, and introduced into compressor 129. Atleast part of the compressed CO2 130 is admitted into injection well 108a/108 b. If any CO2 remains, it may be further purified in purifier 131,then sent to storage, to a local pipeline, or used for EOR 132.

In one embodiment, a Rankine cycle may be employed as follows.Combustion device 110 may be thermally linked to a steam generationdevice 138. Steam generation device 138 may produce steam stream 133,which is introduced into steam turbine 134. Steam turbine 134 producespower 122 and outputs lower pressure steam. This low pressure steam maybe condensed, thereby producing condensate stream 135. Condensate stream135 may be introduced to pump 136, thereby producing higher pressurecondensate stream 137 which is returned to the steam generation device138.

Turning now to FIG. 2, enhanced oil recovery system 200 is provided.Essentially pure liquid oxygen stream 201 is introduced and increased inpressure in pump 202. The pressurized oxygen is vaporized in vaporizer203. At least part of the oxygen is directed into stream 205 andintroduced into combustion turbine combustor 208. The remainingpressurized and vaporized oxygen 204 is then injected into the oilreservoir through an injection well 206 a/206 b in order to supportin-situ combustion. The pressure at which the vaporized oxygen isintroduced into the reservoir may be between about 50% and about 80% ofthe breakdown pressure. Natural gas stream 207 is blended with high LHVfuel gas stream 218 (discussed below) and introduced into combustor 208.

A blended stream 209, containing at least oil, gas and water, isrecovered from production well 210 This blended stream is separated inseparator 211 thereby producing recovered oil stream 212, and separatedwater stream 213. Separated water stream 213 may be used as waterinjection into injection well 206 a/206 b. Recovered gas 214, which mayinclude CO2, CO, H2O, CH4, light hydrocarbons, H2, and H2S, isintroduced to separator 215. The exact composition of the recovered gaswill depend on the nature of the produced oil and the recovery processitself. The recovered gas will be substantially free of nitrogen, due tothe oxygen injection. Separator 215 may include, but is not limited to,the following processes: adsorption, absorption, cryogenic systems andmembrane systems. The adsorption systems may include, but are notlimited to, Rectisol, Selexol, or Amine wash systems. In one embodiment,the membrane system or the combination of cryogenics and membrane systemis preferred. A high LHV fuel gas 216, and a stream that ispredominantly composed of CO2 217 are recovered from separator 215. Thehigh LHV fuel gas 216 may optionally be further purified in gaspurification unit 218. The purified high LHV gas 219 may be combinedwith natural gas stream 207, prior to admission to combustor 208.

After combusting the oxygen stream 205 with the fuel gas streams (207,219), combustion turbine (Brayton cycle) (223, 208, 224) outputs power230 to the process (compression) facility. The exhaust stream 225 thatis predominantly H2O and CO2, impurities being SOx, NOx and Oxygen,exits expander 223. Exhaust stream 225 then enters separator 220, whichoutputs H2O stream 226 and CO2 stream 231 The H2O stream 226 is thencombined with water stream 213 prior to admission into injection well206 a/206 b. Additives can be used in order to control PH Stream 226 CO2stream 231 is then combined with stream 217, partially purified, andintroduced into compressor 224. At least part of the compressed CO2 isadmitted into injection well 206 a/206 b. If any CO2 remains, 228, itmay be further purified in purifier 221, then sent to storage, to alocal pipeline, or used for EOR 222.

The skilled artisan will recognize that the reinjected CO2 will improvein-situ combustion process by improving sweep efficiency. The presentinvention will also improve ultimate oil recovery (miscible/immiscibleflooding will act in addition to in-situ combustion). The synergetic CO2co-injection will reduce O2 needs and improve process economics. The CO2will improve process safety by diluting O2 at the production well

In one embodiment, at least a part of the CO2 228 is further purified221 (to meet pipeline/use specification) and compressed to be exportedfor storage or can constitute a economically valuable gas supply toadditional EOR-EGR-ECBM sites. The present invention also applies tofeedstock such as heavy oil, bitumen, petcoke, kerogene, and coal. Thisprocess can also be applied to biomass or coal and petcoke used asfeedstock of a liquid fuel production process.

What is claimed is:
 1. A liquid fuel production method comprising:introducing a first essentially pure oxygen stream into a structurecontaining a carbonaceous substance, said structure comprising at leastone inlet line and at least one outlet line, initiating and sustainingcombustion in the vicinity of said inlet line, allowing to upgrade suchcarbonaceous substance in order to produce oil; providing a powergeneration system, wherein said power generation system comprises acombustion device, introducing a second essentially pure oxygen streamand a hydrocarbon-containing fuel gas stream into said combustiondevice, wherein said combustion device produces an exhaust gas streamcomprising water and carbon dioxide, separating said exhaust gas streaminto a stream of essentially pure water, and a stream of essentiallypure carbon dioxide, and introducing at least a portion of saidessentially pure carbon dioxide stream into said carbonaceous substancecontaining structure during said combustion.
 2. The liquid fuelproduction method of claim 1, wherein said power generation systemcomprises a Rankine cycle, wherein said Rankine cycle comprises acombustion device, a steam generation device, and a steam turbinegenerator.
 3. The liquid fuel production method of claim 1, wherein saidpower generation system comprises a Brayton cycle, wherein said Braytoncycle comprises a combustion device, an expander, and a compressor.